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KPA500 - Full Power Keydown

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KPA500 - Full Power Keydown

How long can you run the full 500 Watts for (duration)?

I know the Manual states "Duty Cycle at 500 Watts 10 minutes key down / 5 minutes standby"
For those running Full power Keydown modes (SSTV, ETC) what has been your experience?

Thank you

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Michael Eberle

Re: KPA500 - Full Power Keydown

I have run JT65 at full power without any problems, but I manually set
the minimum fan speed to 6 during transmit. May not be necessary but I
don't like for things to get any warmer than necessary.

Mike
KI0HA

On 4/25/2015 3:33 AM, Harry Yingst via Elecraft wrote:
> How long can you run the full 500 Watts for (duration)?
>
> I know the Manual states "Duty Cycle at 500 Watts 10 minutes key down / 5 minutes standby"
> For those running Full power Keydown modes (SSTV, ETC) what has been your experience?
>
>
> Thank you
>
>

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NK7Z

Re: KPA500 - Full Power Keydown

Are you saying you run JT65 at 500 Watts?
--
Thanks and 73's,
For equipment, and software setups and reviews see:
www.nk7z.net
for MixW support see;
http://groups.yahoo.com/neo/groups/mixw/info
for Dopplergram information see:
http://groups.yahoo.com/neo/groups/dopplergram/info
for MM-SSTV see:
http://groups.yahoo.com/neo/groups/MM-SSTV/info

On Sat, 2015-04-25 at 05:06 -0400, Michael Eberle wrote:

> I have run JT65 at full power without any problems, but I manually set
> the minimum fan speed to 6 during transmit. May not be necessary but I
> don't like for things to get any warmer than necessary.
>
> Mike
> KI0HA
>
> On 4/25/2015 3:33 AM, Harry Yingst via Elecraft wrote:
> > How long can you run the full 500 Watts for (duration)?
> >
> > I know the Manual states "Duty Cycle at 500 Watts 10 minutes key down / 5 minutes standby"
> > For those running Full power Keydown modes (SSTV, ETC) what has been your experience?
> >
> >
> > Thank you
> >
> >
>
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Bill-3

Re: KPA500 - Full Power Keydown

In reply to this post by Elecraft mailing list

I often use mine on AM and have never experienced a problem. By the way,
I get good signal reports too!

Bill W2BLC K-Line

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k6dgw

Re: KPA500 - Full Power Keydown

In reply to this post by Elecraft mailing list

You "can" run 500 W forever. Most of us do, it seems

Fred K6DGW
Auburn CA

Harry Yingst via Elecraft <[hidden email]> wrote:

>How long can you run the full 500 Watts for (duration)?
>
>I know the Manual states "Duty Cycle at 500 Watts 10 minutes key down / 5 minutes standby"
>For those running Full power Keydown modes (SSTV, ETC) what has been your experience?
>
>
>Thank you
>
>
>
>
>
>______________________________________________________________
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Bill-3

Re: KPA500 - Full Power Keydown

That is the advantage of having the KPA500 along with the KAT500 - it
turns your K3 into a 500 Watt XCVR.

Last time that was available was the Swan 500 series and the
Hallicrafters SR-500 Tornado. The former was an affordable high power
rig that sometimes developed a serious drifting problem and the latter
was a really fine rig - produced near the end of that company's
manufacturing run. Hallicrafters did also build the SR-2000 Hurricane
(2Kw using 8122 tubes) - another fine rig of that era.

Over the years I owned both of those Hallicrafters rigs and used to wish
that I had kept one or the other. Now that I have the K-Line, there is
no need. I have the 500 Watt XCVR and all the advantages that
microprocessing affords us in the new rigs.

I am not sure that I would buy a KPA2000 or similar, if it was
available. I find that 500 Watts really does me just fine.
But............ I am not a DXer or contest op.

Bill W2BLC K-Line

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Johnny Siu

KPA500 - Full Power Keydown

May be I would like to ask the question from another angle. Can KPA500 be used for RTTY in a contest condition say at 500W? If not, do we need to turn it down to 300W?
Can anyone share with real life experience of using KPA500 in RTTY contest?
73
Johnny VR2XMC

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Elecraft mailing list

Re: KPA500 - Full Power Keydown

In reply to this post by k6dgw

500w Forever as in set a brick on the key and walk away???

From: Fred C. Jensen <[hidden email]>
To: Harry Yingst <[hidden email]>; "[hidden email]" <[hidden email]>
Sent: Saturday, April 25, 2015 9:37 AM
Subject: Re: [Elecraft] KPA500 - Full Power Keydown

You "can" run 500 W forever. Most of us do, it seems

Fred K6DGW
Auburn CA

Harry Yingst via Elecraft <[hidden email]> wrote:

Oliver Dröse

Re: KPA500 - Full Power Keydown

In reply to this post by Johnny Siu

Johnny,

not only that, it will even do it with 600 and 700 watts output. Been
there done that. ;-)

73, Olli - DH8BQA

Contest, DX & radio projects: http://www.dh8bqa.de

Am 25.04.2015 um 16:55 schrieb Johnny Siu:

> May be I would like to ask the question from another angle. Can KPA500 be used for RTTY in a contest condition say at 500W? If not, do we need to turn it down to 300W?
> Can anyone share with real life experience of using KPA500 in RTTY contest?
> 73
> Johnny VR2XMC
>
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Wes (N7WS)

Re: KPA500 - Full Power Keydown

In reply to this post by Johnny Siu

Repetitively calling a station in a DX pileup isn't much different from a contest. I use mine at 500 W with no problem.

Wes. N7WS

On Apr 25, 2015, at 7:55 AM, Johnny Siu <[hidden email]> wrote:

mcduffie

Re: KPA500 - Full Power Keydown

In reply to this post by Michael Eberle

On Sat, 25 Apr 2015 05:06:28 -0400, Michael Eberle wrote:

> I have run JT65 at full power without any problems, but I manually set
> the minimum fan speed to 6 during transmit.

That's a tad extreme. That's 45 second transmit and 75 second receive - more
than enough time to cool down even with fan set to NORM, and not reach speed 6
on its own. When I'm on FSK441 on 6 meters, I sometimes set it to 5 to help
keep it from going to the highest speed at the end of a cycle while running
500+W. That's 30 seconds transmit and 30 seconds receive. It tends to cool to
58-59 degrees before the next cycle. The overall swing is around 12-15 degrees
after 5-10 minutes. Sometimes, a QSO may take 45 minutes, even multiple hours
to complete a full exchange. It can also be as short as 3-5 minutes to get the
reports across and acknowledgements received.

I don't know what Elecraft's opinion is on this, and would be curious to know. I
tend to think that, since the temp is going to get up high anyway, I'd rather
not let it get too cool during the receive cycle. I'm not sure that letting the
temp cycle high and then real low is a good thing. Is it good to cycle wide, or
keep the width of the cycle a little narrower? Power fade with high temp is
also a factor.

Gary
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Mike K2MK

Re: KPA500 - Full Power Keydown

In reply to this post by Johnny Siu

Hi Johnny,

Here is my experience and my opinion.

Yes you can run the KPA500 in a RTTY contest at 500 watts calling CQ and working stations hour after hour. I've done it and it works just fine. The fan automatically increases speed as necessary. It tends to stabilize at speed 5 and only goes to speed 6 for short periods of time.

Since Elecraft put in 6 fan speeds and since speed 6 has the ability to quickly cool it back down to speed 5 then I am of the opinion that I am operating the amplifier within its design limits.

My antennas are resonant and my SWR is low.

73,
Mike K2MK

Johnny Siu wrote

May be I would like to ask the question from another angle. Can KPA500 be used for RTTY in a contest condition say at 500W? If not, do we need to turn it down to 300W?
Can anyone share with real life experience of using KPA500 in RTTY contest?
73
Johnny VR2XMC

Jim Brown-10

Re: KPA500 - Full Power Keydown

In reply to this post by Johnny Siu

On Sat,4/25/2015 7:55 AM, Johnny Siu wrote:
> Can KPA500 be used for RTTY in a contest condition say at 500W? If not, do we need to turn it down to 300W?
> Can anyone share with real life experience of using KPA500 in RTTY contest?

I have done that many times, and have posted that IN THIS THREAD. When
the KPA500 was in beta test, I was loaned a KPA500 for the weekend of a
major RTTY contest and told to "run it with all the lights lit." I did,
and it worked great. I bought one as soon as I could, and regularly run
it in RTTY contests with all the lights lit. According to my calibrated
LP-100A wattmeter, I get more than 600W out into a matched load on all
bands except 6M, where I get at least 500W.

The KPA500 is VERY well protected. The fan will speed up as the output
devices warm up, and if the SWR is too high, drive will be reduced by a
voltage divider and output power will be reduced. In an RTTY contest, if
you're in Run mode (calling CQ) and getting answers to most calls, the
fan will run at a medium speed. If you're not getting answers, it will
get loud, but the amp will keep on going at full power.

I run JT65 and other WSJT modes on 6M for weak signal work, mostly at
full power. Likewise, I run JT65 on 160M, at power levels anywhere
between 10W and 600W, depending on conditions. Again, the KPA500 gives
me full power. The fan will usually speed up a bit near the end of a
JT65 transmission.

To correct a perceived misunderstanding about JT65 and operating power.
JT65 is a WEAK SIGNAL mode, NOT a QRP mode. On the HF bands, it is
considered good practice to run fairly low power on JT65, JT9, and PSK31
so that stations with lousy receivers are not overloaded, and also
because these modes have good enough noise rejection that relatively
little power is needed IF you have decent antennas, and IF both stations
have relatively little RX noise. A good USB sound card can easily
improve JT65 decoding by more than 10 dB -- that's 10X the power.

An example -- a year or so ago, I ran a sked with a guy in ND on 160M. I
have very good TX and RX antennas on 160M with a Tascam US100 USB sound
card, and I heard him just fine, even though he was running only about
50W. As I recall, his signal was about -12 or -14. But he didn't hear me
at 40W, 100W, 200W. I had to go to 400W to get over his RX noise! This
is not uncommon -- I can often decode 8-10 signals per pass on 160M,
many of them from east of Chicago, with signals in the range of -14 to
-20, but I've got to run 400-500W to get them to hear me. By contrast,
NO3M, whose 160M station in western PA has very good RX antennas,
consistently hears me running 5W on CW.

73, Jim K9YC (near Santa Cruz, CA)

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Kevin Stover

Re: KPA500 - Full Power Keydown

In reply to this post by Elecraft mailing list

All of this anecdotal eveidence is interesting but meaningless.

Elecratf advertise and rate the amp as a 500W amp. Not 600, not 700. Someone should put the amp on an spectrum analyser while running at 700 wats to see whatr it looks like while being overdriven.

Elecraft have also said, in the operating manual, that the time limnit is 10 minutes key down. Did they put that line in the manual just to take up space or is it purely CYA?

Jusdt because some people are overdriving the amp and getting away with it doesn't mean it was designed for it.

R. Kevin Stover
AC0H
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Lyle Johnson

Re: KPA500 - Full Power Keydown

In reply to this post by Johnny Siu

The KPA500 RF deck and power supply can put out 500 watts for a very
long time (definition of "very long time" is an exercise left for the
reader).

If you are operating outdoors in direct sunlight in Saudi Arabia at
mid-day in the summer, key down time is likely limited to a few
minutes. If the heat sink is covered in dust from a recent wind storm,
it may only be several seconds.

If you are operating at the south pole in winter with a direct air duct
to the outside to draw cooling air over the KPA500 heatisnk, you can
probably operate key down for months -- and might need to to prevent the
amplifier from being damaged by the extreme cold!

The point is that this is a thermal management problem. If you keep the
ambient air environment around the amplifier at a comfortable room
temperature and ensure the fan and vents on the amplifier cabinet are
not blocked, you can probably operate it at 500 watts as long as you
have patience to hold the key down. If the ambient air is not
sufficient to cool the power transistors, perhaps due to temperature or
limits on air flow, the amplifier will eventually shut down to protect
itself.

Like many things in life, this is a system (ham shack station design
including physical environment) issue, not a component (amplifier) issue.

73,

Lyle KK7P

> May be I would like to ask the question from another angle. Can KPA500 be used for RTTY in a contest condition say at 500W? If not, do we need to turn it down to 300W?

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N7US

Re: KPA500 - Full Power Keydown

I keep my KAT500 under my KPA500 to not impede the airflow from the
amplifier, as recommended in the manual.

73, Jim N7US

-----Original Message-----

The KPA500 RF deck and power supply can put out 500 watts for a very long
time (definition of "very long time" is an exercise left for the reader).

If you are operating outdoors in direct sunlight in Saudi Arabia at mid-day
in the summer, key down time is likely limited to a few minutes. If the
heat sink is covered in dust from a recent wind storm, it may only be
several seconds.

If you are operating at the south pole in winter with a direct air duct to
the outside to draw cooling air over the KPA500 heatisnk, you can probably
operate key down for months -- and might need to to prevent the amplifier
from being damaged by the extreme cold!

The point is that this is a thermal management problem. If you keep the
ambient air environment around the amplifier at a comfortable room
temperature and ensure the fan and vents on the amplifier cabinet are not
blocked, you can probably operate it at 500 watts as long as you have
patience to hold the key down. If the ambient air is not sufficient to cool
the power transistors, perhaps due to temperature or limits on air flow, the
amplifier will eventually shut down to protect itself.

Like many things in life, this is a system (ham shack station design
including physical environment) issue, not a component (amplifier) issue.

73,

Lyle KK7P

> May be I would like to ask the question from another angle. Can KPA500 be
used for RTTY in a contest condition say at 500W? If not, do we need to
turn it down to 300W?

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Elecraft mailing list

Re: KPA500 - Full Power Keydown

In reply to this post by Kevin Stover

Agreed
I'm looking for people who actually run it at 500 watts in SSTV, or other like modes (not voice)
A SSTV picture can take 110 seconds (Less or more depending on encoding, but 110 seconds is common as Scottie 1)

From: Kevin Stover <[hidden email]>
To: Harry Yingst <[hidden email]>
Cc: Harry Yingst via Elecraft <[hidden email]>
Sent: Saturday, April 25, 2015 2:21 PM
Subject: Re: [Elecraft] KPA500 - Full Power Keydown

All of this anecdotal eveidence is interesting but meaningless.

Elecratf advertise and rate the amp as a 500W amp. Not 600, not 700. Someone should put the amp on an spectrum analyser while running at 700 wats to see whatr it looks like while being overdriven.

Elecraft have also said, in the operating manual, that the time limnit is 10 minutes key down. Did they put that line in the manual just to take up space or is it purely CYA?

Jusdt because some people are overdriving the amp and getting away with it doesn't mean it was designed for it.

R. Kevin Stover
AC0H

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Jim Brown-10

Re: KPA500 - Full Power Keydown

In reply to this post by Kevin Stover

On Sat,4/25/2015 11:21 AM, Kevin Stover wrote:
> All of this anecdotal eveidence is interesting but meaningless.

Is it? The original post asked who had actually used the KPA500 that
way. He got several responses, including mine.

> Elecratf advertise and rate the amp as a 500W amp. Not 600, not 700.

I stated my experience. The difference between 500W and 600W is 0.8 dB.
The difference between 500W and 650W is 1.1 dB.

Early versions of K3 firmware allowed it to cranked to 120 W. That was
reduced to 110 W to place an upper limit on IMD.

> Someone should put the amp on an spectrum analyser while running at 700 wats to see whatr it looks like while being overdriven.

You can bet that Elecraft did that throughout the design process, and
probably in final test of the power modules. I know the guy who did that
testing. :) I've done it myself. It remains clean at the highest power
I can get out of it, which varies a bit depending on the load Z between
600W and 700W. I've published a link to those measurements several
times on this reflector.
k9yc.com/P3_Spectrum_Measurements.pdf and
k9yc.com/FTDX5000_Report.pdf

The highest power in these reports is 550W, but I've measured up to 650W
and the sidebands get slightly wider (5-10%) and a few dB stronger.

> Elecraft have also said, in the operating manual, that the time limnit is 10 minutes key down. Did they put that line in the manual just to take up space or is it purely CYA?

That's a reasonable spec based on my observations with a thousand or
more hours of use.

>
> Jusdt because some people are overdriving the amp and getting away with it doesn't mean it was designed for it.

It's pretty difficult to overdrive the KPA500 -- if you supply more
drive than it wants, it will insert an attenuator between the input
connector and the power amp stage to keep the power within design
parameters. Protection circuitry in the K3, KX3, KPA500, and KAT500 is
set to prevent destructive overheating and keep the signal clean.

On Sat,4/25/2015 12:04 PM, Harry Yingst via Elecraft wrote:
> I'm looking for people who actually run it at 500 watts in SSTV, or other like modes (not voice) A SSTV picture can take 110 seconds

If it will do 500W keydown for 10 minutes, it will do 110 seconds for
SSTV. :)

73, Jim K9YC

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Johnny Siu

KPA500 - Full Power Keydown

Thanks, Jim and all the elecrafters responded to my question about using KPA500 under full power in RTTY contest.
Some of the answers came to me under private emails off the list. I would like to thank them as well.
From all the responses, KPA500 is a solid performer under full power in all modes including those high duty cycle.
I mostly operate SSB so that I do not have much chances to operate KPA500 under high duty cycle. Hence, I put up my question in this email listing.
73
Johnny VR2XMC
寄件人︰ Jim Brown <[hidden email]>
收件人︰ [hidden email]
傳送日期︰ 2015年04月26日 (週日) 5:02 AM
主題︰ Re: [Elecraft] KPA500 - Full Power Keydown

On Sat,4/25/2015 11:21 AM, Kevin Stover wrote:
> All of this anecdotal eveidence is interesting but meaningless.

Is it? The original post asked who had actually used the KPA500 that
way. He got several responses, including mine.

> Elecratf advertise and rate the amp as a 500W amp. Not 600, not 700.

I stated my experience. The difference between 500W and 600W is 0.8 dB.
The difference between 500W and 650W is 1.1 dB.

Early versions of K3 firmware allowed it to cranked to 120 W. That was
reduced to 110 W to place an upper limit on IMD.

> Someone should put the amp on an spectrum analyser while running at 700 wats to see whatr it looks like while being overdriven.

You can bet that Elecraft did that throughout the design process, and
probably in final test of the power modules. I know the guy who did that
testing. :) I've done it myself. It remains clean at the highest power
I can get out of it, which varies a bit depending on the load Z between
600W and 700W. I've published a link to those measurements several
times on this reflector.
k9yc.com/P3_Spectrum_Measurements.pdf and
k9yc.com/FTDX5000_Report.pdf

The highest power in these reports is 550W, but I've measured up to 650W
and the sidebands get slightly wider (5-10%) and a few dB stronger.

> Elecraft have also said, in the operating manual, that the time limnit is 10 minutes key down. Did they put that line in the manual just to take up space or is it purely CYA?

That's a reasonable spec based on my observations with a thousand or
more hours of use.

>
> Jusdt because some people are overdriving the amp and getting away with it doesn't mean it was designed for it.

It's pretty difficult to overdrive the KPA500 -- if you supply more
drive than it wants, it will insert an attenuator between the input
connector and the power amp stage to keep the power within design
parameters. Protection circuitry in the K3, KX3, KPA500, and KAT500 is
set to prevent destructive overheating and keep the signal clean.

On Sat,4/25/2015 12:04 PM, Harry Yingst via Elecraft wrote:
> I'm looking for people who actually run it at 500 watts in SSTV, or other like modes (not voice) A SSTV picture can take 110 seconds

If it will do 500W keydown for 10 minutes, it will do 110 seconds for
SSTV. :)

73, Jim K9YC

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W7CS

Re: KPA500 - Full Power Keydown

In reply to this post by Elecraft mailing list

To add to K9YC's comments:

EME QSOs are completed in really "weak signal" conditions, especially
those via CW. WSJT digital modes have apparently have greatly helped
smaller stations (and "no code Experts) make contacts (not
necessarily QSOs, by my definition).

Here QRO+ power levels improves the success rate. Often with HB
PAs. The FCC statement " only enough power need to provide
communications", has some meaning here !

W7CS

To correct a perceived misunderstanding about JT65 and operating power.
JT65 is a WEAK SIGNAL mode, NOT a QRP mode. On the HF bands, it is
considered good practice to run fairly low power on JT65, JT9, and PSK31
so that stations with lousy receivers are not overloaded, and also
because these modes have good enough noise rejection that relatively
little power is needed IF you have decent antennas, and IF both stations
have relatively little RX noise. A good USB sound card can easily
improve JT65 decoding by more than 10 dB -- that's 10X the power.

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